Packet-switched networks are increasingly used for industrial control application thanks to the introduction of Layer-2 features that allow the transport of control data that cannot suffer latency and transfer delay variation. For instance, low-latency sampling data, control (in closed loop) and image streaming (e.g. image processing) have very stringent latency requirements. Image streaming and associated processing as a part of a control loop has greater requirements than best effort transport could provide in a converged network.
In parallel, best effort stream is not time-critical, but provides a constant source of interference stream. Solutions have been progressively developed, in particular for the adaptation of switched Ethernet to the requirements of industrial field busses: EtherCAT, Ethernet Powerlink, TCnet, PROFINET, etc. All these solutions rely on specific additions to the standard Ethernet protocol that provide support for scheduled streams.